Embodiments of the present application relate generally to a refractometer. Particularly, certain embodiments relate to a refractometer for measuring the content of solute in a liquid.
Referring to FIG. 8 (taken from Japanese Patent Gazette No. 2004-150923), a digital refractometer 200 is shown. The refractometer has a prism 202, a light source 204, and a light-receiving sensor 206. The light source 204 projects light to the interface between a sample liquid S and the prism 202. Light is reflected from the interface at an angle determined by the index of refraction of the sample liquid S. The reflected light is received by the light-receiving sensor 206 and converted to an electrical signal. From this signal, it may be possible to determine the refractive index of the liquid. Since the refractive index of a liquid is related to the content of the substance dissolving in the liquid, refractometers can be used as a tool for measuring the concentration of soluble substance in a liquid—e.g. as a saccharometer for measuring sugar content. Such devices may be used to evaluate the sugar content of grocery produce, for example.
The refractometer 200 is designed in such a way that the sample liquid S is to be dripped on the prism 202 for measurement. However, the refractometer 200 may not function effectively if it is immersed in the sample liquid S. Furthermore, since the face 202a of the prism 202 that touches the sample liquid S is deeper than the sample stable 208 surrounding the face 202a, the refractometer 200 may be unable to function effectively when the prism 202 is brought in contact with a part of a piece of grocery produce, such as the cross-section of an orange.
Thus, there is a need for a refractometer capable of measuring a refractive index of a liquid when immersed at least partially in the liquid. Further, there is a need for a refractometer to operate by touching or bringing it into contact with a liquid bearing item, such as grocery produce.